1. Field of the Invention
This invention relates to a gas turbine power generation system, particularly to a gas turbine power generation system that uses a generator power source comprising a single-spool micro gas turbine engine whose compressor and turbine are coaxially aligned.
2. Description of the Related Art
The term “micro gas turbine” or “micro turbine” is commonly used to refer to a gas turbine power generation system whose generator is driven by a single-spool gas turbine engine including a coaxially aligned compressor and turbine. In recent years, the micro gas turbine has attracted attention for its utility as an electric power generation means for multifamily housing units, high-rise apartment buildings, factories, large retail stores, leisure facilities, schools, hospitals and the like.
In this type of gas turbine power generator, the engine is supplied with air through an air intake stage including a filter and duct. Technology relating to such an air intake stage is set out, for example, in Japanese Laid-Open Patent Application No. 2000-220463.
This kind of gas turbine power generator requires regular maintenance, such as periodic replacement of the turbine and air filter. To facilitate this work, US-based Capstone Turbine Corporation (http://www.microturbine.com), for example, offers a gas turbine generator that, as shown in FIG. 18, increases maintenance efficiency by use of a structure that enables the main unit 202 of the generator 200 to be slid frontward (downward in the drawing) and out of the housing 204. (FIG. 18 is a simplified top view of the generator 200.)
Regulations require that a gas turbine generator be installed so as to leave a prescribed amount of open space on the side used to conduct inspection and maintenance and in front of the air inlet. Since the spool-type gas turbine engine is relatively long in the direction of the rotating shaft, however, a side parallel to the rotating shaft should preferably be made openable so as to obtain a large open area for maintenance work.
For structural reasons, on the other hand, the air inlet of the air intake stage is usually formed so as to center on an extension of the axis of the engine rotating shaft. Thus, conventionally, the air inlet and the maintenance access opening have been provided on different faces of the gas turbine generator. This is inconvenient because it requires open spaces to be left on two sides and therefore increases the total dedicated space required for the installation.
A gas turbine engine intakes and exhausts more air/gas per unit time than a reciprocating engine and therefore requires a larger air filter. The work of changing the air filter is therefore more troublesome.
Further, when installing the gas turbine generator referred to above, it is best to reserve (dedicate) at least a total amount of space equal to the size of the housing 204 plus the space 206 occupied by the housing 204 when it is slid fully forward and a space 208 for carrying out maintenance. More efficient space utilization is obviously desirable. Moreover, for maximum maintenance ease it is preferable to also reserve the space 210 so that the main unit 202 can be accessed for maintenance from both sides. This further aggravates the inconvenience of having to dedicate a large space for the installation.
In addition, the gas turbine power generator has a number of noise sources that produce, for instance, air intake noise, exhaust noise, and engine rotation noise. However, low-noise (quiet) operation is preferable, especially when the gas turbine power generator is installed to supply electric power at a residential, school or hospitable facility. While noise can be reduced by using large amounts of sound-absorbing material and by lengthening the duct of the air intake system and installing an interposed silencer, these measures increase the size of the generator and also the amount of installation space.
It should also be noted that gas turbine generators are often installed outdoors, e.g., on a roof, because the temperature of the exhaust gas is higher than that of reciprocating engine-driven generators. For reducing installation space, it is therefore effective to decrease not only height but also footprint. The easiest way to reduce the footprint of a single-spool gas turbine engine would be to install it with the longer axial direction standing upright (with the rotating shaft in the direction of gravity (vertical direction)). As the spool-type gas turbine engine is difficult to install vertically for technical reasons, however, installation is generally horizontal (with the rotating shaft lying horizontal). The resulting long length of generator in the horizontal direction has therefore tended to make the footprint large.
In light of the foregoing, a need has been felt for gas turbine generators of this type that are better in maintenance ease, lower in noise (quieter) and smaller (more compact) in installation (dedicated) space. However, these points conflict with one another, as can be seen, for example, from the fact that installation (dedicated) space increases when priority is given to maintenance ease. Conventional gas turbine generators have failed to respond to all of these needs simultaneously.